Elias Hanna, MD
Posterior Infarction:
-When accompanied by inferior or lateral STEMI, posterior infarction is easily recognized, but it can be difficult to diagnose when it occurs alone, the so-called true posterior STEMI.
-ST-segment depression that is most prominent in any of the leads V1 through V3 often indicates posterior STEMI rather than non–ST-elevation ACS and indicates the need for emergency reperfusion.
-On the other hand, ST-segment depression that is greatest in leads other than V1-V3 is more indicative of diffuse subendocardial ischemia (non-ST-elevation ACS).
-If a patient has persistent true angina and ST-segment depression in leads V1-V3, record leads V7-V9 to confirm the dg and perform emergent reperfusion (thrombolysis or PCI).
V7-V9 will have ST-segment elevation and possibly Q waves.
Also, if a patient has persistent angina and a non-diagnostic ECG, record leads V7-
V9. ST-segment elevation in those leads may be the only ECG indicator of ischemia
(usually LCx ischemia).
-Large and/or wide R wave in leads V1 or V2 supports the dg of posterior infarction but is only seen in ~50% of the cases. Large R is reciprocal to posterior Q in this context.
Causes of large R wave in V1 or V2:
Diagnosis
RVH
Confirmatory clues
Right axis deviation
Right atrial enlargement
ST depression and T inversion in V1-V2
RBBB
Posterior MI
QRS wide> 120 msec (>100 msec if incomplete RBBB)
ST depression in V1-V3 but T upright (≠RVH)
ST elevation and/or Q waves in V7-V9
WPW Short PR, delta wave, widened QRS
Normal variant Large R wave in V1-V2 is the only abnormality on ECG